Passing High Sided Vehicles - Suction with Caravan Towing

[Saxo Appeal]

Has anyone experienced some really bad suction when passing trucks or high sided vehicles?

Driving the Caravan last week and the suction pulled the caravan that much I looked into the left passenger mirror and the van was nearly hitting the front cab of a lorry.

Pretty sure the lorry had to break, but the caravan didn't hit it thank goodness 🙏

I was doing 60 at the time, but the suction was really bad and I felt a bit shaky afterwards as that could have ended up being worse.

Can I ask what everyone else does in this situation? I thought about when passing a truck on left side, move more to the right to compensate for the suction.

We have an 8 meter Caravan being pulled by an Audi SQ5, so it is a rather long vehicle.

 

[Woodentop]

My secret is to push them around. If I see a large vehicle coming up behind in the lane to my right to overtake, I gently drift out towards the white line which will make the truck move out as well. Then when he gets up to my van I drift rather more quickly back to the left white line which leaves a bigger gap between us..
Works a treat.

 

[borderbilly]

When I drove wagons, the double decker high ones, it was always clenched bum time when I overtook other articles. Just hold on tight!

 

[otherclive]

When being passed by trucks, coaches or faster moving large vehicles I would move to the left of lane 1. With a 7m overall length caravan I can’t recall having an experience similar to yours. Perhaps the truck may have inadvertently moved to the right of lane 1. Certainly moving right in your lane would help the issue. Were you being passed by faster traffic at the time as the combination of truck wind age and passing traffic wind age might have exacerbated the situation. Or could a side wind have affected your outfit. There’s no specific answer other than moving to the right of lane2 and being aware of what’s around you.

 

[borderbilly]

My secret is to push them around. If I see a large vehicle coming up behind in the lane to my right to overtake, I gently drift out towards the white line which will make the truck move out as well. Then when he gets up to my van I drift rather more quickly back to the left white line which leaves a bigger gap between us..
Works a treat.

That's a bit naughty, and very dangerous.

 

[ProfJohnL]

Unfortunately you have experienced one of the main reasons why I always suggest caravanners should go for the smallest possible caravan that will meet their needs, caravan should be considered as difficult trailers to manage. Big caravan present a large "sail" area, and will be more affected by aerodynamics of other vehicles when they pass each other. Basically you need to drive to give as much room as possible between you and the other vehicle.

Incidentally it's the same effect but at 90 degrees to that which aircraft use to fly, and Formula 1 cars seek to create down force, speed and separation are significant factors , so consider slowing down.

 

[GUMPY]

Nothing that large ever overtakes me 😁

 

[Saxo Appeal]

The truck wasn’t taking over me, it was a 3 lane Motorway

The truck was doing about 55 in the first lane, and I overtook it moving into the 2nd lane and then passing it. Then just as I was about fully passed the caravan was sucked towards it on left side mirror, and indeed it was a bum clencher as I watched it moving towards the trucks cabin.

 

[otherclive]

The truck wasn’t taking over me, it was a 3 lane Motorway

The truck was doing about 55 in the first lane, and I overtook it moving into the 2nd lane and then passing it. Then just as I was about fully passed the caravan was sucked towards it on left side mirror, and indeed it was a bum clencher as I watched it moving towards the trucks cabin.

Moving to the right in your lane would reduce the suction force, but there are no guarantees that it may not happen again. As I said in my post above vehicles passing in lane 3, wind conditions and even perturbations in the carriageway could initiate a suction sway whilst you are overtaking the HGV in lane 1. I found car transporters the worst for turbulence. Of course we are assuming that the truck did not move across lane 1 towards your outfit. Thus initiating your sway.

 

[Sam Vimes]

My secret is to push them around. If I see a large vehicle coming up behind in the lane to my right to overtake, I gently drift out towards the white line which will make the truck move out as well. Then when he gets up to my van I drift rather more quickly back to the left white line which leaves a bigger gap between us..
Works a treat.

Seems rather dangerous to me as you're hoping the other vehicle will see what you're doing and take action.

 

[RogerL]

Seems rather dangerous to me as you're hoping the other vehicle will see what you're doing and take action.

I seem to recall that it is/was the advice of the Caravan Club to do just that on multi-lane roads.

 

[GUMPY]

I sidel to the right when overtaking
Van just on the offside white line.
Seems to help but not every time.
But that could be cos I'm towing at 105%

 

[Hutch]

I have had this happen, and very frightening.
It is Bernoulli's principle, the theory that makes aircraft, wings and carburettors work.
It also causes ships to come together when travelling very close and parallel to each other if refuelling at sea.

 

[borderbilly]

The truck wasn’t taking over me, it was a 3 lane Motorway

The truck was doing about 55 in the first lane, and I overtook it moving into the 2nd lane and then passing it. Then just as I was about fully passed the caravan was sucked towards it on left side mirror, and indeed it was a bum clencher as I watched it moving towards the trucks cabin.

Was the truck carrying vacuum cleaner's?

 

[CrewOVtwo]

I experienced this many times whilst driving both a 7.5 tonne high sided vehicle and whilst towing a caravan

The best advice I can give is, firstly maintain your concentration, and if you are being overtaken then maximise your gap between the vehicle overtaking you by keeping towards the side of your lane nearest the hard shoulder........

And if you are the vehicle that is doing the overtaking, maximise your gap between the vehicle you are overtaking by keeping towards the outer side of your lane........

There are a few other points to note.

1. If you are being overtaken, don't be afraid to slow down a notch as you move towards the inside portion of your lane.

2. Don't be afraid to not bother overtaking - if you're on a motorway and travelling a similar speed to a HGV then the time advantage you will gain by passing one is highly unlikely to save you more than a few seconds in time gained.

3. Be fastidious about nose weight and loading of your caravan. This will help minimise, but not eliminate, the effect that you mentioned.

I've just thought of a fourth thing that might help.
Take a driving course by the 'Institute of Advanced Motorists'. I did that about 42 years ago, and although I may have an accident tomorrow, I've not had one in all that time - I definitely feel the lessons I learned from them have contributed to my level of luck in avoiding a crash.

 

[otherclive]

I have had this happen, and very frightening.
It is Bernoulli's principle, the theory that makes aircraft, wings and carburettors work.
It also causes ships to come together when travelling very close and parallel to each other if refuelling at sea.

You mean like this ? June 1973 HMS Intrepid transferring to HMS Glamorgan off Turkey.

 

[Buckman]

I found car transporters the worst for turbulence. Of course we are assuming that the truck did not move across lane 1 towards your outfit. Thus initiating your sway.

When over taking a car transporter, I am extra vigilant as you can feel the turbulence even before commencing the over take.

 

[Challenger]

When over taking a car transporter, I am extra vigilant as you can feel the turbulence even before commencing the over take.

I find that car transporters are the worst. Seeing one is ' buttock clenching' !

 

[JTQ]

I tend to settle for travelling with the HGVs only opting to overtake where there is plenty of space or the road speed is reduced, like climbing hills.

Afterall, its only when they are travelling at near maximum allowed speed the suction issue dominates, so it hardly slows us down till a safe option comes available.

The massive physical bulk of some HGVs these days, coupled with their ability to travel at significant speeds that makes these aerodynamic issues inevitable. All part of the learning curve, gaining towing experience.

 

[Buckman]

My thoughts are that as HGV is travelling it is creating a "buffer" zone at the front of it. This "buffer" pushes out a vehicle overtaking. The driver of the over taking vehicle feels the vehicle being "pushed" and countermands this by pushing against it using the steering wheel. A natural reflex and not really noticeable.

When they pass the "buffer" zone area created by the front of the HGV, the driver is still "pushing" against the steering wheel which then causes the over taking vehicle to feel as if it is being sucked in when in reality they are not being sucked in.

Just my thoughts and probably wrong.

 

[izzy]

Ours is only a short 2 berth and copes very well with lorry bow waves when I am either passing or being passed
Coaches on the other hand are a different ball game as they never seem to consider what effect that their higher speed may have on anything.
I always try to steer clear of them, literally

 

[Buckman]

Ours is only a short 2 berth and copes very well with lorry bow waves when I am either passing or being passed
Coaches on the other hand are a different ball game as they never seem to consider what effect that their higher speed may have on anything.
I always try to steer clear of them, literally

Where possible, if I see them coming I move over to the left as far as possible. I am not sure at what speed they are allowed to legally travel?

 

[Lutz]

I've found that overtaking high sided vehicles on a trailing throttle helps. I accelerate a bit as I approach them then lift my foot off the accelerator pedal as I pass, and resume as before when the overtaking manoeuvre has been accomplished.

 

[RogerL]

Where possible, if I see them coming I move over to the left as far as possible. I am not sure at what speed they are allowed to legally travel?

Coaches are allowed to do 70 mph on motorways, 60 mph on other dual carriageways and 50 mph on single carriageways - so on motorways they can legally overtake towing vehicles.

 

[Dustydog]

CrewOVtwo hit the right notes.

Saxo total outfit length is virtually the same as mine. Since we’ve had the TA the incidents of suction have become a rarity.
Towing ratio 67%. and as you know all correctly loaded to typical PCv obsession😉
The few times I have felt a suck was a coach that was overtaking faster than I anticipated. No twitch or movement. The previous SA definitely gave the experience a worth while exclamation.
I suspect most people are caught out by an element of surprise. In reality I believe they feel the shock wave and automatically twitch the steering wheel . It this that causes a lot of the sensation, ie an over correction.

The real devil in the detail is the crosswind that hits you when you come out of a cutting onto say a long high bridge or embankment. Now that can be scary.